Structural “decoration” of plastic products replicated from nanoimprinted steel inserts

Structural colouration is a well-known “bio-inspired” phenomenon that explains the astonishing natural iridescence of several animals’ skin, such as: fish scales, birds’ feathers, butterflies’ wings, flowers and more beauties in nature. The phenomenon occurs when light diffracts due to the topology of the just mentioned surfaces independently from radiation-based colouring or pigmentation. In recent years, the rise of nanotechnology has brought about the possibility to design and reproduce structural colours on consumer products [1]. In this study, structural colours are proposed as decorative features for plastic substrates. Periodic sub-micro gratings showing a variable pitch (400 – 1500 nm) and step height (300 – 1000 nm) are manufactured in a cleanroom by means of nanoimprinting lithography on steel inserts. Gratings are subsequently replicated on plastic products by means of polymer injection moulding. This study focuses on understanding the technology readiness, highlighting limitations and advantages of the adoption of structural colours in plastic consumer products. Aspects related to different polymer replication techniques of the nanostructures, metrological challenges to ensure manufacturing accuracy and precision of the mentioned features, the durability of the plastic gratings and the durability of the nanoimprinted injection moulding inserts would be key factors in understanding the applicability of structural decoration in the plastic industry.